Introduce sal::systools::CoTaskMemAllocated to use RAII for CoTaskMemFree

Change-Id: I5553138bfc8dd989e68b8bcc2be981746e8c1e84
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/150783
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/systools/win32/comtools.hxx b/include/systools/win32/comtools.hxx
index b141842882aa..d54b1a22ce02 100644
--- a/include/systools/win32/comtools.hxx
+++ b/include/systools/win32/comtools.hxx
@@ -240,6 +240,25 @@ namespace sal::systools
         T* com_ptr_;
     };
 
+    // A class to use with functions taking an out pointer argument,
+    // that needs to be freed with CoTaskMemFree - like SHGetKnownFolderPath
+    template <typename T> class CoTaskMemAllocated
+    {
+    public:
+        ~CoTaskMemAllocated() { CoTaskMemFree(m_pv); }
+
+        T** operator&()
+        {
+            CoTaskMemFree(std::exchange(m_pv, nullptr));
+            return &m_pv;
+        };
+
+        operator T*() { return m_pv; }
+
+    private:
+        T* m_pv = nullptr;
+    };
+
 } // sal::systools
 
 /* Typedefs for some popular COM interfaces */